Tunnel boring machine

Abstract

To provide a tunnel excavator capable of improving cutting performance or excavation performance by a hard tip of a center bit.SOLUTION: The tunnel boring machine 100 includes a cutter head 1 and a plurality of cutter bits 2 including a center bit 23 disposed on the innermost peripheral side in the radial direction of a rotation center position Pc (rotation center axis). The center bit 23 includes a base member 231, and a first hard tip 232 attached to the base member 231 and having a side surface extending in a direction parallel to the radial direction (R direction) and including a first cut / excavated surface 232a that cuts or excavates at least one of soil and an obstacle in the ground. The first cut excavation surface 232a of the first hard tip 232 is disposed at a position shifted radially outward from the rotation center position Pc so as not to include the rotation center position Pc of the cutter head 1 when viewed from the boring direction side, and is disposed on the most boring direction side.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a tunnel boring machine equipped with a cutter head. [Background technology]

[0002] BACKGROUND ART Conventionally, a tunnel boring machine equipped with a cutter head is known (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 discloses a tunnel boring machine equipped with a cutter head. This tunnel boring machine is equipped with an earth and sand cutting bit, an obstacle cutting bit, and a center bit. The cutter head is configured to rotate by being driven by a drive motor and to move forward in the excavation direction. Each of the earth and sand cutting bit, obstacle cutting bit, and center bit is configured to cut or excavate earth and sand, obstacles, etc. ahead as the cutter head rotates and moves forward.

[0004] The center bit in Patent Document 1 is a bit that is placed on the central axis of rotation of the cutter head. The center bit includes a main body (base material) and a carbide tip. When viewed from the excavation direction, the carbide tip is arranged linearly along the radial direction of the central axis of rotation so as to pass through the center of rotation of the cutter head. The part of the carbide tip that passes through the center of rotation is the tip-most part of the linear carbide tip on the excavation direction side. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6104617 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the tunnel boring machine of Patent Document 1, the carbide tip of the center bit has a portion that is positioned at the rotation center of the cutter head. The portion that passes through the rotation center of the carbide tip is the most distal portion of the carbide tip in the excavation direction. For this reason, at the most distal portion that passes through the rotation center of the carbide tip, the rotational speed (circumferential speed) of the carbide tip associated with the rotation of the cutter head is low (approximately zero), making it difficult to cut or excavate soil and obstacles ahead, resulting in low cutting or excavation performance by the carbide tip of the center bit. Therefore, there is a need to improve the cutting or excavation performance of the carbide tip (hard tip) of the center bit.

[0007] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide a tunnel boring machine that can improve the cutting performance or excavation performance using the hard tip of the center bit. [Means for solving the problem]

[0008] In order to achieve the above object, the tunnel boring machine of the present invention comprises a cutter head that excavates as it rotates, and a center bit that is arranged radially innermost of the central axis of rotation of the cutter head, and a plurality of cutter bits that are arranged on the excavation direction side of the cutter head, the center bit including a base material and a first cutting and excavation surface that is a side extending in a direction parallel to the radial direction and cuts or excavates at least one of soil and sand and obstacles underground, and a first hard tip that is attached to the base material, and the first cutting and excavation surface of the first hard tip is arranged in a position that is shifted radially outward from the rotation center position of the cutter head when viewed from the excavation direction side so as not to include the rotation center position, and is arranged on the excavation direction side.

[0009] In the tunnel boring machine of the present invention, as described above, the first cutting and excavation surface of the first hard tip of the center bit is arranged at a position radially outward from the rotation center position of the cutter head when viewed from the excavation direction side, and is arranged at the furthest side in the excavation direction so as not to include the rotation center position of the cutter head. In this way, the first cutting and excavation surface of the first hard tip arranged furthest side in the excavation direction is arranged at a position radially outward from the rotation center position so as not to include the rotation center position of the cutter head, so that the rotational speed associated with the rotation of the cutter head can be prevented from becoming approximately 0 at the first cutting and excavation surface of the first hard tip arranged furthest side in the excavation direction. As a result, even the first cutting and excavation surface of the first hard tip arranged furthest side in the excavation direction can cut and excavate earth and obstacles (such as steel) ahead, and therefore the cutting performance or excavation performance of the hard tip of the center bit can be improved compared to when the hard tip of the center bit is arranged at the rotation center position of the cutter head.

[0010] In the tunnel boring machine according to the above aspect, the entire first hard tip is preferably arranged so as not to include the position of the center of rotation of the cutter head when viewed from the excavation direction side. By configuring in this way, by arranging the entire first hard tip so as not to include the position of the center of rotation of the cutter head, it is possible to prevent the rotational speed of the entire first hard tip associated with the rotation of the cutter head from becoming approximately 0, and therefore it is possible to improve the cutting performance or excavation performance of the first hard tip.

[0011] In the tunnel boring machine according to the above aspect, the center bit is preferably arranged such that, when viewed from the excavation direction, its center position is shifted radially outward from the center of rotation of the cutter head. By configuring in this manner, simply by shifting the center position of the center bit, it is possible to easily achieve a center bit structure in which the rotational speed associated with the rotation of the cutter head does not become approximately zero.

[0012] In the tunnel boring machine according to the above aspect, preferably, the first hard tip further includes a first tip face provided on the excavation direction side of the first cutting and excavation surface, and the center bit further includes a second hard tip including a second tip face arranged on the opposite side of the excavation direction from the first tip face, and the second tip face of the second hard tip is arranged to include the rotation center position of the cutter head when viewed from the excavation direction side. With this configuration, earth and obstacles on the rotation center position side of the cutter head that are not cut by the first cutting and excavation surface that is offset from the rotation center position can be crushed by the second tip face of the second hard tip, and therefore the uncut earth and obstacles can also be sent rearward (in the opposite direction to the excavation direction) in a crushed state.

[0013] In this case, the base material of the center bit preferably has a stepped shape including a first portion provided on the excavation direction side and to which the first cutting and excavation surface of the first hard tip is attached, and a second portion provided on the opposite side of the excavation direction from the first portion and to which the second tip surface of the second hard tip is attached. With this configuration, simply by making the base material of the center bit stepped, it is possible to realize a structure in which the second tip surface of the second hard tip is positioned to include the rotation center position of the cutter head and is positioned on the opposite side of the excavation direction from the first tip surface, making it easy to realize a base material structure for the center bit in which the second hard tip is positioned.

[0014] In a tunnel boring machine equipped with a center bit including the above-described stepped base material, preferably, the depth of the stepped shape of the base material of the center bit is less than half the length from the bottom surface to the first tip end face of the first hard tip in the excavation direction of the first hard tip. With this configuration, even if the base material has a stepped shape, more than half the length of the first hard tip from the bottom surface to the first tip end face can be held by the base material, so the first hard tip can be reliably held by the base material.

[0015] In a tunnel boring machine equipped with a center bit further including the above-mentioned second hard tip, preferably, the first tip face of the first hard tip and the second tip face of the second hard tip are arranged side by side in the radial direction when viewed from the excavation direction side. With this configuration, the first hard tip can be held by the base material provided on both sides of the first tip face of the first hard tip in the circumferential direction about the rotation center axis of the cutter head, and the second hard tip can be held by the base material provided on both sides of the second tip face of the second hard tip, so that each of the first hard tip and the second hard tip can be reliably held by the base material.

[0016] In a tunnel boring machine equipped with a center bit including the above-described stepped base material, preferably, the first portion of the stepped base material includes a step surface provided at the boundary with the second portion, and the center bit further includes a third hard tip attached to the step surface. With this configuration, the third hard tip can protect the step surface from earth and sand and obstacles that hit the step surface as the cutter head rotates, thereby preventing chipping of the step surface portion of the base material.

[0017] In this case, the third hard tip preferably includes a second cutting and excavation surface that is a side surface extending in a direction parallel to the radial direction and is located on the opposite side of the excavation direction from the first tip end surface of the first hard tip. With this configuration, the second cutting and excavation surface of the third hard tip can cut or excavate at least one of earth and sand and obstacles, thereby further improving the cutting or excavation performance of the hard tip of the center bit.

[0018] In the tunnel boring machine according to the above aspect, preferably, the first hard tip further includes a first tip surface provided on the excavation direction side of the first cutting and excavation surface, and the first tip surface of the first hard tip has a flat surface extending in a direction perpendicular to the excavation direction. With this configuration, since the first tip surface has a flat surface, when the cutter head moves in the excavation direction, the load received from earth and obstacles can be prevented from concentrating in one place on the tip portion of the first hard tip, and chipping of the tip portion of the first hard tip can be suppressed.

[0019] In the tunnel boring machine according to the above aspect, the first hard tip preferably further includes a first tip surface provided on the excavation direction side of the first cutting and excavation surface, and an inclined surface provided on the radial outer periphery of the first tip surface and inclined in the opposite direction to the excavation direction. With this configuration, chips of at least one of the cut earth and sand and obstacles can be made to flow along the inclined surface, so that the chips can be effectively flowed into the chamber inside the cutter head.

[0020] In a tunnel boring machine equipped with a center bit including the above-mentioned stepped base material, preferably, the first portion of the stepped base material includes a step surface provided at the boundary with the second portion, and the first hard tip further includes an inner parallel surface provided on the step surface and extending parallel to the direction opposite to the excavation direction from the inner side in the radial direction of the first tip surface. With this configuration, the force of the first hard tip in the excavation direction associated with movement of the cutter head in the excavation direction can be concentrated on the tip portion of the first hard tip, so that the part of the inner parallel surface exposed by the stepped shape can be easily bitten into soil and obstacles. [Effects of the Invention]

[0021] According to the present invention, as described above, the cutting performance or excavation performance of the hard tip of the center bit can be improved. [Brief explanation of the drawings]

[0022] [Figure 1]1 is a cross-sectional side view of a tunnel boring machine according to a first embodiment. FIG. [Figure 2] FIG. 2 is a front view of the cutter head of the tunnel boring machine according to the first embodiment, viewed from the excavation direction side. [Figure 3] FIG. 2 is a front view of the center of the cutter head of the tunnel boring machine according to the first embodiment, viewed from the excavation direction side. [Figure 4] FIG. 2 is a perspective view of a center bit of the tunnel boring machine according to the first embodiment. [Figure 5] FIG. 2 is a front view of the center bit of the cutter head of the tunnel boring machine according to the first embodiment, viewed from the excavation direction side. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7] FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 5. [Figure 8] FIG. 2 is a front view of the center bit as seen from the excavation direction, showing the area around the rotation center position of the cutter head of the tunnel boring machine according to the first embodiment and the area around the center position of the center bit. [Figure 9] FIG. 10 is a front view of the cutter head of a tunnel boring machine according to a second embodiment, as viewed from the excavation direction side. [Figure 10] FIG. 10 is a perspective view of a center bit of a tunnel boring machine according to a second embodiment. [Figure 11] FIG. 10 is a front view of a cutter head of a tunnel boring machine according to a modification of the first and second embodiments, viewed from the excavation direction side. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0024] [First embodiment] A tunnel boring machine 100 according to a first embodiment will be described with reference to FIGS.

[0025] (Tunnel Boring Machine) In each drawing, the direction parallel to the rotation center position Pc (rotation center axis) of the tunnel boring machine 100, which extends along the excavation direction (front-rear direction), is indicated as the X direction. Of the X directions, the excavation direction (forward) is indicated as the X1 direction, and the other direction (rearward) is indicated as the X2 direction. The straight line extending along the X direction and passing through the rotation center position Pc is the rotation center axis.

[0026] In each figure, the left-right direction is indicated by the Y direction. Within the Y direction, the right side is indicated by the Y1 direction, and the left side is indicated by the Y2 direction. In each figure, the up-down direction is indicated by the Z direction. Within the Z direction, the up side is indicated by the Z1 direction, and the down side is indicated by the Z2 direction. In each figure, the radial direction of the tunnel boring machine 100 is indicated by the R direction. Within the radial direction, the direction facing radially outward is indicated by R1, and the direction facing radially inward is indicated by R2. In each figure, the circumferential direction of the tunnel boring machine 100 is indicated by the θ direction. Within the circumferential direction, one side is indicated by θ1, and the other side is indicated by θ2.

[0027] As shown in FIG. 1, the tunnel boring machine 100 includes a cutter head 1 , a plurality of cutter bits 2 , a boring machine body 3 , and a shield jack 4 .

[0028] (Cutter head and cutter bit) The cutter head 1 is configured to excavate as it rotates. As shown in Figure 2, the cutter head 1 includes a central portion 11, a plurality of cutter spokes 12, a plurality of sub-spokes 13, an intermediate ring 14, and an outer ring 15.

[0029] Each of the multiple cutter spokes 12 extends radially from the central portion 11. Each of the multiple sub-spokes 13 is disposed between adjacent cutter spokes 12 in the θ direction. Each of the multiple sub-spokes 13 is attached to an intermediate ring 14 and an outer ring 15. That is, the inner circumferential side (R2 direction side) of each of the multiple sub-spokes 13 is attached to the intermediate ring 14. The outer circumferential side (R1 direction side) of each of the multiple sub-spokes 13 is attached to the outer circumferential ring 15. Each of the intermediate ring 14 and the outer circumferential ring 15 has a circular shape when viewed from the excavation direction side (X1 direction side). The intermediate ring 14 is disposed radially inside (R2 direction side) of the outer circumferential ring 15.

[0030] As shown in FIG. 1, the cutter head 1 is configured to rotate in the θ direction around a rotation center position Pc (rotation center axis) by a drive motor (not shown). The cutter head 1 is configured to excavate forward (in the X1 direction) by a shield jack 4. Multiple cutter bits 2 are provided on the front surface (the surface facing the X1 direction) of the cutter head 1. The multiple cutter bits 2 are configured to cut or excavate at least one of soil and sand and obstacles underground as the cutter head 1 rotates and excavates. The soil and obstacles cut by the multiple cutter bits 2 flow into a chamber 1a inside the cutter head 1 and are mixed with the mud-making material in the chamber 1a. In this way, the natural ground is excavated by the multiple cutter bits 2.

[0031] The plurality of cutter bits 2 will be described in detail later.

[0032] (Excavator body) The excavator main body 3 includes a body 31, a bending jack 32, a partition wall 33, a screw conveyor 34, and an erector 35. The body 31 is a cylindrical member. A working space 31a is provided within the body 31. The bending jack 32 is provided within the body 31. The partition wall 33 is configured to separate a chamber 1a within the front cutter head 1 from the working space 31a within the body 31. The screw conveyor 34 is configured to discharge earth and sand within the chamber 1a toward the working space 31a. The erector 35 is configured to build a ring of segments Seg that will become the tunnel wall.

[0033] (Shield Jack) The shield jack 4 is configured to generate a thrust by pressing the segments Seg. The tunnel boring machine 100 excavates forward due to the reaction force of this pressing force.

[0034] (Detailed configuration of cutter bit) 2, the cutter bit 2 includes a plurality of obstacle cutting bits 21, a plurality of earth excavation bits 22, and a center bit 23. The plurality of obstacle cutting bits 21, the plurality of earth excavation bits 22, and the center bit 23 are fixed to the front surface (the surface on the X1 direction side) of the cutter head 1 by welding. Note that the plurality of obstacle cutting bits 21, the plurality of earth excavation bits 22, and the center bit 23 may also be fixed to the front surface (the surface on the X1 direction side) of the cutter head 1 by bolting instead of welding.

[0035] The plurality of obstacle cutting bits 21 are arranged in a row in the R direction. The plurality of earth excavation bits 22 are arranged in a row in the R direction.

[0036] At least one of cutting obstacles and excavating earth and sand is performed by the plurality of obstacle cutting bits 21, and excavating earth and sand is performed by the plurality of earth excavation bits 22. Note that a switching mechanism (not shown) may be used to switch between two states: a state in which obstacles are cut by the plurality of obstacle cutting bits 21 (obstacle cutting state), and a state in which earth and sand are excavated by the plurality of earth excavation bits 22 (earth excavation state).

[0037] (Center bit) The center bit 23 is the bit of the cutter bit 2 that is arranged on the innermost side in the R direction of the cutter head 1. The center bit 23 is provided in the central part 11 of the cutter head 1. The center bit 23 is arranged on the side of the cutter bit 2 that is closest to the excavation direction (X1 direction) in the excavation direction (X1 direction). The center bit 23 is configured to be the first of the cutter bits 2 to perform at least one of cutting obstacles and excavating earth and sand in the excavation direction (X1 direction).

[0038] As shown in FIGS. 3 and 4, the center bit 23 includes a base material 231, a first hard tip 232, a second hard tip 233, and a third hard tip 234.

[0039] <Base material> As shown in Fig. 4, the base material 231 is formed of a material that is tougher than the first hard tip 232, the second hard tip 233, and the third hard tip 234. The base material 231 is formed of a steel material such as S45C. When viewed from the excavation direction side (X1 direction side), the outer peripheral surface of the base material 231 is formed of a circumferential portion Sr1 with a central angle greater than 180 degrees and a straight portion Sr2 connecting both ends of the circumferential portion Sr1. The base material 231 has a first portion 231a, a second portion 231b, a first recess 231c, a second recess 231d, and a third recess 231e.

[0040] The base material 231 has a stepped shape including a first portion 231a and a second portion 231b. The first portion 231a is provided on the X1 direction side of the base material 231. The second portion 231b is provided on the X2 direction side of the first portion 231a of the base material 231. In the stepped base material 231, the first portion 231a is a convex portion that protrudes in the X1 direction from the second portion 231b, and the second portion 231b is a portion that is recessed in the X2 direction from the first portion 231a.

[0041] The first portion 231a of the stepped base material 231 includes a step surface St1 provided at the boundary with the second portion 231b. The step surface St1 extends along the X direction. The step surface St1 is a flat surface. The second portion 231b of the stepped base material 231 includes a step surface St2 on the X1 direction side. The step surface St2 extends along the R direction. The step surface St2 is a flat surface. The step surface St1 is an example of a "step surface" in the claims.

[0042] The first portion 231a is attached to the cutting and excavating surface 232a of the first hard tip 232. The first portion 231a is attached to the cutting and excavating surface 234a of the third hard tip 234. The second portion 231b is attached to the tip surface 233a of the second hard tip 233. The second portion 231b is attached to the cutting and excavating surface 234a of the third hard tip 234.

[0043] The first recess 231c is recessed from the surface of the first portion 231a on the X1 direction side toward the X2 direction. The first hard tip 232 is fitted into the recessed first recess 231c, and the first hard tip 232 is attached. The first portion 231a has an inclined surface SL1 on its surface on the X1 direction side. The inclined surface SL1 is inclined toward the X2 direction in accordance with the inclination angle of the inclined surface 232c of the first hard tip 232. The inclination angle of the inclined surface SL1 is, for example, 25 degrees or more and 35 degrees or less. The inclined surface SL1 is inclined toward the X2 direction from the end of the step surface St1 on the X1 direction side. The inclined surface SL1 is a surface that curves in the X1 direction as it approaches the inner periphery.

[0044] The second recess 231d is recessed from the surface on the X1-direction side of the second part 231b toward the X2-direction side. The second hard tip 233 is fitted into the recessed second recess 231d and is attached thereto. The second part 231b has an inclined surface SL2 as the surface on the X1-direction side. The inclined surface SL2 is inclined toward the X2-direction in accordance with the inclination angle of the inclined surface 233b of the second hard tip 233. The inclination angle of the inclined surface SL2 is, for example, 25 degrees or more and 35 degrees or less. The inclined surface SL2 is inclined from the end on the R1-direction side of the step surface St2 toward the X2-direction side. The inclined surface SL2 is a curved surface positioned in the X1-direction as it is closer to the inner peripheral side.

[0045] The third recess 231e is recessed from the surface on the X1-direction side of the first part 231a and the surface on the X1-direction side of the second part 231b toward the X2-direction side. The third hard tip 234 is fitted into the recessed third recess 231e and is attached thereto. The second part 231b has an inclined surface SL3 as the surface on the X1-direction side. The inclined surface SL2 is inclined toward the X2-direction in accordance with the inclination angle of the inclined surface 234c of the third hard tip 234. The inclination angle of the inclined surface SL3 is, for example, 25 degrees or more and 35 degrees or less. The inclined surface SL3 is inclined from the end on the R1-direction side of the step surface St2 toward the X2-direction side. The inclined surface SL3 is a curved surface positioned in the X1-direction as it is closer to the inner peripheral side.

[0046] As shown in FIGS. 5 and 6, the depth De of the stepped shape of the base material 231 of the center bit 23 is smaller than half of the length Lb from the bottom surface to the tip surface 232b of the first hard tip 232 in the X-direction (drilling direction) of the first hard tip 232 (De < Lb / 2). The depth De of the stepped shape of the base material 231 of the center bit 23 is, for example, 15 mm or more and 25 mm or less.

[0047] (The first hard tip) As shown in FIGS. 5 and 6, the first hard tip 232 is formed of a material harder than the base material 231. The first hard tip 232 is formed of, for example, a cemented carbide alloy. The first hard tip 232 is configured to cut or excavate at least one of underground soil and obstacles. The first hard tip 232 has a cutting / excavating surface 232a, a tip surface 232b, an inclined surface 232c, and an inner circumferential parallel surface 232d. The cutting / excavating surface 232a is an example of a "first cutting / excavating surface" in the claims. The tip surface 232b is an example of a "first tip surface" in the claims.

[0048] The cutting portion of the center bit 23 in the first embodiment closest to the X1 direction is positioned at a position offset in the R1 direction from the rotation center position Pc. That is, the cutting and excavation surface 232a of the first hard tip 232 is positioned at a position offset in the R1 direction from the rotation center position Pc. Specifically, the cutting and excavation surface 232a of the first hard tip 232 is positioned at a position offset radially outward (in the R1 direction) from the rotation center position Pc of the cutter head 1 so as not to include the rotation center position Pc of the cutter head 1 when viewed from the excavation direction (X1 direction) side, and is positioned at the furthest side in the excavation direction (X1 direction) (see FIG. 7). In other words, the first hard tip 232 is not positioned on the rotation center position Pc. Furthermore, the entire first hard tip 232 is positioned so as not to include the rotation center position Pc of the cutter head 1 when viewed from the excavation direction (X1 direction). Furthermore, the first hard tip 232 protrudes in the X1 direction from the base material 231.

[0049] This structure for shifting the cutting excavation surface 232a is achieved by shifting the center position Pb (rotation center axis) of the center bit 23 in the R1 direction from the rotation center position Pc of the cutter head 1 when viewed from the excavation direction (X1 direction). The center position Pb of the center bit 23 is not the center of gravity when viewed from the excavation direction (X1 direction), but is the center position in the R direction of the maximum diameter part of the center bit 23 when viewed from the excavation direction (X1 direction). A line (rotation center axis) extending in the X direction that passes through the rotation center position Pc and a line extending in the X direction that passes through the center position Pb are parallel to each other.

[0050] 5, in the R direction, the tip of the cutting and excavation surface 232a of the first hard tip 232 on the R2 direction side is shifted by a shift amount Gap from the rotation center position Pc of the cutter head 1. The shift amount Gap is, for example, not less than 10 mm and not more than 30 mm.

[0051] The cutting excavation surfaces 232a are provided on each of the θ1 direction and the θ2 direction of the inner circumferential parallel surface 232d. Each of the pair of cutting excavation surfaces 232a is a side surface extending along a direction parallel to the R direction. The pair of cutting excavation surfaces 232a are arranged at approximately the same offset position in the R direction. An R chamfer is formed on the R2 direction side portion of each of the pair of cutting excavation surfaces 232a.

[0052] The tip surface 232b is provided on the excavation direction (X1 direction) side of the cutting and drilling surface 232a. The tip surface 232b has a flat surface extending along the R direction (see Figure 7). The inclined surface 232c is provided on the radial outer periphery side (R1 direction side) of the tip surface 232b. The inclined surface 232c is inclined in the opposite direction to the excavation direction (X2 direction). The inclination angle of the inclined surface 232c is, for example, 25 degrees or more and 35 degrees or less. The inner periphery parallel surface 232d is provided on the step surface St1. The inner periphery parallel surface 232d extends from the tip surface 232b in the opposite direction to the excavation direction (X2 direction). The inner periphery parallel surface 232d is the part on the inner periphery side (R1 direction side) in the radial direction.

[0053] (Second hard tip) As shown in FIG. 5, the second hard tip 233 is formed of a material harder than the base material 231. The second hard tip 233 is formed of, for example, a cemented carbide alloy. The second hard tip 233 is configured to cut or excavate at least one of underground soil and obstacles. The second hard tip 233 has a tip surface 233a and an inclined surface 233b. The tip surface 233a is an example of a "second tip surface" in the claims.

[0054] When viewed from the excavation direction side (X1 direction side), the tip surface 233a of the second hard tip 233 is arranged so as to include the rotation center position Pc of the cutter head 1. In other words, the second hard tip 233 extends from the end of the base material 231 on the R1 direction side in the R2 direction so as to exceed the rotation center position Pc of the cutter head 1.

[0055] 6, the tip surface 233a of the second hard tip 233 is positioned on the side opposite the excavation direction (X2 direction side) from the tip surface 232b. The tip surface 233a of the second hard tip 233 is positioned on the excavation direction side (X1 direction side) from the step surface St2. The tip surface 233a of the second hard tip 233 is the surface on the excavation direction side (X1 direction side) of the second hard tip 233. The tip surface 233a has a flat surface extending along the R direction (see FIG. 7).

[0056] The inclined surface 233b is provided on the radially outer periphery (R1 direction side) of the tip surface 233a. The inclined surface 233b is inclined in the opposite direction to the excavation direction (X2 direction). The inclination angle of the inclined surface 233b is, for example, 25 degrees or more and 35 degrees or less.

[0057] (Third hard tip) As shown in FIG. 5, the third hard tip 234 is formed of a material harder than the base material 231. The third hard tip 234 is formed of, for example, a cemented carbide alloy. The third hard tip 234 is configured to cut or excavate at least one of underground soil and obstacles. The third hard tip 234 has a cutting / excavating surface 234a, a tip surface 234b, an inclined surface 234c, and an inner circumferential parallel surface 234d. The cutting / excavating surface 234a is an example of a "second cutting / excavating surface" in the claims.

[0058] The third hard tip 234 is attached to the base material 231 so as to straddle the step surface St1 and the step surface St2. The third hard tip 234 is attached to the base material 231 so as to straddle the first portion 231a and the second portion 231b.

[0059] The cutting and excavating surface 234a of the third hard tip 234 is disposed at a position shifted in the R1 direction from the rotation center position Pc. Specifically, the cutting and excavating surface 234a of the third hard tip 234 is disposed at a position shifted radially outward (in the R1 direction) from the rotation center position Pc of the cutter head 1 so as not to include the rotation center position Pc when viewed from the excavation direction (X1 direction).

[0060] The cutting and excavating surfaces 234a are provided on each of the θ1 and θ2 directions of the inner circumferential parallel surface 234d. Each of the pair of cutting and excavating surfaces 234a is a surface extending along a direction parallel to the R direction. The pair of cutting and excavating surfaces 234a are arranged at approximately the same offset position in the R direction. As shown in FIG. 6, the pair of cutting and excavating surfaces 234a are arranged on the opposite side of the excavation direction (X2 direction side) from the tip surface 232b of the first hard tip 232. The pair of cutting and excavating surfaces 234a include at least a portion that is arranged between the tip surface 232b of the first hard tip 232 and the tip surface 233a of the second hard tip 233 in the excavation direction (X1 direction). An R-chamfer is formed on the R2 direction side portion of each of the pair of cutting and excavating surfaces 234a.

[0061] As shown in FIG. 7, the tip surface 234b is provided on the excavation direction (X1 direction) side of the cutting and drilling surface 234a. The tip surface 234b has a flat surface extending along the R direction. The inclined surface 234c is provided on the radial outer periphery (R1 direction side) of the tip surface 234b. The inclined surface 234c is inclined in the opposite direction to the excavation direction (X2 direction). The inclination angle of the inclined surface 234c is, for example, 25 degrees or more and 35 degrees or less. The inner periphery parallel surface 234d is provided on the step surface St1 and the step surface St2. The inner periphery parallel surface 234d extends from the tip surface 234b in the opposite direction to the excavation direction (X2 direction). The inner periphery parallel surface 234d is the part on the inner periphery side (R1 direction side) in the radial direction.

[0062] (Relationship between the first, second and third hard tips) As shown in Fig. 8, when viewed from the excavation direction (X1 direction), the direction along the linear center line C1 passing through the rotation center position Pc and the center position Pb is defined as direction A. Furthermore, center line C2 is a straight line extending along direction B passing through center position Pb. In the following explanation, the direction perpendicular to direction A when viewed from the excavation direction (X1 direction) is defined as direction B.

[0063] As shown in FIG. 8, the first hard tip 232 and the second hard tip 233 are arranged side by side in the radial direction (R direction) when viewed from the excavation direction (X1 direction). Furthermore, the tip face 232b of the first hard tip 232 and the tip face 233a of the second hard tip 233 are arranged side by side in the radial direction (R direction) when viewed from the excavation direction (X1 direction). Furthermore, a gap Ma is provided in the radial direction (R direction) between the first hard tip 232 and the second hard tip 233 when viewed from the excavation direction (X1 direction). The gap Ma is, for example, about 5 mm. The third hard tip 234 is arranged between the first hard tip 232 and the second hard tip 233 in the θ2 direction when viewed from the excavation direction (X1 direction). Moreover, the first hard tip 232, the second hard tip 233, and the third hard tip 234 are arranged at equal angular intervals (approximately 90 degree intervals) in the θ direction when viewed from the excavation direction (X1 direction) side.

[0064] The length Lr1 of the first hard tip 232 is longer than both the length Lr2 of the second hard tip 233 and the length Lr3 of the third hard tip 234. The length Lr2 of the second hard tip 233 is shorter than the length Lr1 of the first hard tip 232 and longer than the length Lr3 of the third hard tip 234. The length Lr3 of the third hard tip 234 is shorter than both the length Lr1 of the first hard tip 232 and the length Lr2 of the second hard tip 233.

[0065] The thickness Th1 of the first hard tip 232 is substantially the same as the thickness Th2 of the second hard tip 233 and the thickness Th3 of the third hard tip 234. In the B direction, the first hard tip 232, the second hard tip 233, and the third hard tip 234 have a constant thickness Th1, a constant thickness Th2, and a constant thickness Th3, respectively. The thickness of each of the first hard tip 232, the second hard tip 233, and the third hard tip 234 is the length of each of the first hard tip 232, the second hard tip 233, and the third hard tip 234 in a direction perpendicular to the X direction and the R direction. Each of the thickness Th1 of the first hard tip 232, the thickness Th2 of the second hard tip 233, and the thickness Th3 of the third hard tip 234 is 10 mm or more and 30 mm or less.

[0066] When viewed from the excavation direction side (X1 direction side), the area of ​​the tip face 232b of the first hard tip 232 and the area of ​​the tip face 233a of the second hard tip 233 are approximately the same. When viewed from the excavation direction side (X1 direction side), the area of ​​the tip face 234b of the third hard tip 234 is smaller than both the area of ​​the tip face 232b of the first hard tip 232 and the area of ​​the tip face 233a of the second hard tip 233.

[0067] When viewed from the excavation direction (X1 direction), the first hard tip 232 extends so that direction A is its longitudinal direction. When viewed from the excavation direction (X1 direction), the first hard tip 232 is formed in a rectangular shape with a rounded inner peripheral portion. When viewed from the excavation direction (X1 direction), the first hard tip 232 has a shape that is symmetrical with respect to the center line C1.

[0068] When viewed from the excavation direction (X1 direction), the second hard tip 233 extends so that direction A is its longitudinal direction. When viewed from the excavation direction, the second hard tip 233 is formed in a rectangular shape with a rounded inner peripheral portion. When viewed from the excavation direction, the second hard tip 233 has a shape that is symmetrical with respect to the center line C1.

[0069] When viewed from the excavation direction (X1 direction), the third hard tip 234 extends so that its longitudinal direction is in direction B, which is the direction along the linear center line C2 that is perpendicular to the center line C1. When viewed from the excavation direction (X1 direction), the third hard tip 234 is formed in a rectangular shape with a rounded inner peripheral portion. When viewed from the excavation direction (X1 direction), the third hard tip 234 has a shape that is symmetrical with respect to the center line C2.

[0070] When viewed from the excavation direction (X1 direction), the first hard tip 232 and the second hard tip 233 are arranged on one side in the A direction and the other side in the A direction, respectively, of the center position Pb. In the A direction, the overlap length La1 between the step surface St2 and the first hard tip 232 is smaller than the overlap length La2 between the step surface St2 and the second hard tip 233. When viewed from the excavation direction (X1 direction), the third hard tip 234 is arranged only on one side in the B direction, which is the direction along the center line C2, of the center position Pb.

[0071] When viewed from the excavation direction (X1 direction), on the other side in direction B of the center position Pb, a straight section Sr2 that forms the outer peripheral surface of the base material 231 is located. When viewed from the excavation direction (X1 direction), the center line C2 passes through the center position of the straight section Sr2 and is perpendicular to the straight section Sr2.

[0072] The step surface St1 is a surface extending in a direction perpendicular to the center line C1. When viewed from the excavation direction (X1 direction), the length Lst1 of the step surface St1 in the B direction on one side in the B direction (the side where the third hard tip 234 is arranged) is smaller than the length Lst2 of the step surface St1 in the B direction on the other side in the B direction.

[0073] When viewed from the excavation direction (X1 direction), the first hard tip 232 and the step surface St2 are arranged in the peripheral area Arb adjacent to the center position Pb. The "peripheral area Arb of the center position Pb" is the area near the center position Pb when viewed from the excavation direction (X1 direction), and is the area adjacent to the center position Pb so as to surround the center position Pb. When viewed from the excavation direction (X1 direction), only the second hard tip 233 is arranged in the peripheral area Arc of the rotation center position Pc (rotation center axis). The "peripheral area Arc of the rotation center position Pc" is the area near the rotation center position Pc when viewed from the excavation direction (X1 direction), and is the area adjacent to the rotation center position Pc so as to surround the rotation center position Pc.

[0074] (Effects of the first embodiment) In the first embodiment, the following effects can be obtained.

[0075] In the first embodiment, as described above, the cutting and excavating surface 232a of the first hard tip 232 of the center bit 23 is arranged at a position shifted radially outward (toward the R1 direction) from the rotation center position Pc of the cutter head 1 when viewed from the excavation direction (X1 direction) side so as not to include the rotation center position Pc of the cutter head 1, and is arranged at the furthest side in the excavation direction (X1 direction). As a result, the cutting and excavating surface 232a of the first hard tip 232 arranged furthest on the excavation direction (X1 direction) side is arranged at a position shifted radially outward (toward the R1 direction) from the rotation center position Pc so as not to include the rotation center position Pc of the cutter head 1, so that the rotational speed associated with the rotation of the cutter head 1 can be prevented from becoming approximately 0 on the cutting and excavating surface 232a of the first hard tip 232 arranged furthest on the excavation direction (X1 direction) side. As a result, cutting and excavating of soil and obstacles (such as steel) ahead can be performed even on the cutting and excavation surface 232a of the first hard tip 232, which is positioned furthest in the excavation direction (X1 direction), so the cutting or excavation performance of the hard tip of the center bit 23 can be improved compared to when the hard tip of the center bit 23 is positioned at the rotation center position Pc of the cutter head 1.

[0076] Furthermore, in the first embodiment, as described above, the entire first hard tip 232 is arranged so as not to include the rotation center position Pc of the cutter head 1 when viewed from the excavation direction side (X1 direction side). By thus arranging the entire first hard tip 232 so as not to include the rotation center position Pc of the cutter head 1, it is possible to prevent the rotational speed of the entire first hard tip 232 associated with the rotation of the cutter head 1 from becoming approximately 0, and therefore it is possible to improve the cutting performance or excavation performance of the first hard tip 232.

[0077] Furthermore, in the first embodiment, as described above, the center bit 23 is arranged such that, when viewed from the excavation direction (X1 direction), the center position Pb of the center bit 23 is shifted radially outward (toward the R1 direction) from the rotation center position Pc of the cutter head 1. This makes it possible to easily achieve a center bit 23 structure in which the rotational speed associated with the rotation of the cutter head 1 does not become approximately 0, simply by shifting the center position Pb of the center bit 23.

[0078] Furthermore, in the first embodiment, as described above, the first hard tip 232 includes a tip surface 232b provided on the excavation direction (X1 direction) side of the cutting and excavating surface 232a. The center bit 23 includes a second hard tip 233 including a tip surface 233a located on the opposite side of the excavation direction (X1 direction) from the tip surface 232b. The tip surface 233a of the second hard tip 233 is located so as to include the rotation center position Pc of the cutter head 1 when viewed from the excavation direction (X1 direction) side. This allows the tip surface 233a of the second hard tip 233 to crush earth and sand and obstacles on the side of the rotation center position Pc of the cutter head 1 that are not cut by the cutting and excavating surface 232a that is shifted from the rotation center position Pc.

[0079] Furthermore, in the first embodiment, as described above, the base material 231 of the center bit 23 has a stepped shape including a first portion 231a provided on the excavation direction (X1 direction) side and to which the cutting and drilling surface 232a of the first hard tip 232 is attached, and a second portion 231b provided on the opposite side of the excavation direction (X1 direction) of the first portion 231a and to which the tip surface 233a of the second hard tip 233 is attached. Thus, simply by forming the base material 231 of the center bit 23 into a stepped shape, it is possible to realize a structure in which the tip surface 233a of the second hard tip 233 is positioned to include the rotation center position Pc of the cutter head 1 and is positioned on the opposite side of the excavation direction (X1 direction) from the tip surface 232b, and therefore it is possible to easily realize a structure of the base material 231 of the center bit 23 in which the second hard tip 233 is positioned.

[0080] Furthermore, in the first embodiment, as described above, the depth De of the stepped shape of the base material 231 of the center bit 23 is smaller than half the length Lb from the bottom surface to the tip surface 232b of the first hard tip 232 in the excavation direction (X1 direction) of the first hard tip 232. As a result, even when the base material 231 has a stepped shape, more than half of the length Lb from the bottom surface to the tip surface 232b of the first hard tip 232 can be held by the base material 231, and therefore the first hard tip 232 can be reliably held by the base material 231.

[0081] Furthermore, in the first embodiment, as described above, the tip surface 232b of the first hard tip 232 and the tip surface 233a of the second hard tip 233 are arranged side by side in the radial direction (R direction) when viewed from the excavation direction side (X1 direction side). This allows the first hard tip 232 to be held by the base material 231 provided on both sides of the tip surface 232b of the first hard tip 232 in the circumferential direction (θ direction) around the rotation center position Pc (rotation center axis) of the cutter head 1, and the second hard tip 233 to be held by the base material 231 provided on both sides of the tip surface 233a of the second hard tip 233. Therefore, each of the first hard tip 232 and the second hard tip 233 can be reliably held by the base material 231.

[0082] Furthermore, in the first embodiment, as described above, the first portion 231a of the stepped base material 231 includes a step surface St1 provided at the boundary with the second portion 231b. The center bit 23 includes a third hard tip 234 attached to the step surface St1. This allows the third hard tip 234 to protect the step surface St1 from soil and obstacles that hit the step surface St1 as the cutter head 1 rotates, thereby preventing chipping of the step surface St1 of the base material 231.

[0083] Furthermore, in the first embodiment, as described above, the third hard tip 234 has a side surface extending in a direction parallel to the radial direction (R direction), and includes a cutting and excavating surface 234a that is located on the opposite side of the excavation direction (X2 direction side) from the tip end surface 232b of the first hard tip 232. This makes it possible to cut or excavate at least one of earth and sand and obstacles using the cutting and excavating surface 234a of the third hard tip 234, thereby further improving the cutting or excavation performance of the hard tip of the center bit 23.

[0084] Furthermore, in the first embodiment, as described above, the first hard tip 232 includes a tip surface 232b provided on the excavation direction (X1 direction) side of the cutting and drilling surface 232a. The tip surface 232b of the first hard tip 232 has a flat surface extending in a direction perpendicular to the excavation direction (X1 direction). As a result, because the tip surface 232b has a flat surface, when the cutter head 1 moves in the excavation direction (X1 direction), the load received from earth and sand and obstacles can be prevented from concentrating in one place on the tip portion of the first hard tip 232, and chipping of the tip portion of the first hard tip 232 can be suppressed.

[0085] Furthermore, in the first embodiment, as described above, the first hard tip 232 includes a tip surface 232b provided on the excavation direction (X1 direction) side of the cutting and excavation surface 232a, and an inclined surface 232c provided on the radial outer periphery of the tip surface 232b and inclined in the opposite direction to the excavation direction (X1 direction). This allows chips of at least either the cut earth and sand or obstacles to flow along the inclined surface 232c, so that the chips can be effectively flowed into the chamber 1a in the cutter head 1.

[0086] Furthermore, in the first embodiment, as described above, the first portion 231a of the stepped base material 231 includes a step surface St1 provided at the boundary with the second portion 231b. The first hard tip 232 is provided on the step surface St1 and includes an inner parallel surface 232d on the radially inner side that extends from the tip surface 232b in the direction opposite to the excavation direction (X1 direction). This allows the force of the first hard tip 232 in the excavation direction (X1 direction) associated with movement of the cutter head 1 in the excavation direction (X1 direction) to be concentrated on the tip portion of the first hard tip 232, making it possible to easily bite into soil and obstacles at the portion of the inner parallel surface 232d exposed by the stepped shape.

[0087] [Second embodiment] A second embodiment will be described with reference to Figures 9 and 10. In this second embodiment, a center bit 230 includes a base material 230a, a first hard tip 232, and a second hard tip 233. That is, unlike the center bit 23 of the first embodiment, a third hard tip 234 is not provided. In the drawings, the same components as those of the first embodiment are denoted by the same reference numerals.

[0088] (Tunnel Boring Machine) As shown in FIG. 9, a tunnel boring machine 200 of the second embodiment comprises a cutter head 1, a plurality of cutter bits 2, a boring machine body 3 (see FIG. 1), and a shield jack 4 (see FIG. 1).

[0089] (Detailed configuration of cutter bit) As shown in FIG. 9, the cutter bit 202 includes a plurality of obstacle cutting bits 21, a plurality of earth and sand excavation bits 22, and a center bit 230.

[0090] (Center bit) The center bit 230 is the bit of the cutter bits 202 that is arranged on the innermost side in the R direction of the cutter head 1.

[0091] As shown in FIG. 10, the center bit 230 includes a base material 230 a , a first hard tip 232 , and a second hard tip 233 .

[0092] The base material 230a has a first portion 231a, a second portion 231b, a first recess 231c, and a second recess 231d. The base material 230a has a stepped shape including the first portion 231a and the second portion 231b.

[0093] The cutting and excavation surface 232a of the first hard tip 232 of the second embodiment is disposed at a position shifted in the R1 direction from the rotation center position Pc. The tip end surface 233a of the second hard tip 233 is disposed so as to include the rotation center position Pc of the cutter head 1 when viewed from the excavation direction side (X1 direction side). The first hard tip 232 and the second hard tip 233 are disposed side by side in the radial direction (R direction) when viewed from the excavation direction (X1 direction) side.

[0094] The other configurations of the second embodiment are the same as those of the first embodiment.

[0095] (Effects of the second embodiment) In the second embodiment, the following effects can be obtained.

[0096] In the second embodiment, as in the first embodiment, the cutting and excavating surface 232a of the first hard tip 232 is positioned radially outward (toward the R1 direction) from the rotation center position Pc of the cutter head 1 so as not to include the rotation center position Pc when viewed from the excavation direction (X1 direction), and is positioned closest to the excavation direction (X1 direction). This makes it possible to improve the cutting or excavation performance of the hard tip of the center bit 230.

[0097] Other effects of the second embodiment are the same as those of the first embodiment.

[0098] [Variations] The embodiments and modifications disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims rather than the description of the above embodiments, and further includes all modifications (modifications) within the meaning and scope of the claims.

[0099] For example, in the above first and second embodiments, an example was shown in which the present invention was applied to a mud pressure type tunnel boring machine, but the present invention is not limited to this and may also be applied to a mud water type tunnel boring machine.

[0100] Furthermore, in the above first and second embodiments, an example was shown in which the center bit 23 (230) was arranged so that its center position Pb was shifted radially outward from the rotation center position Pc of the cutter head 1 when viewed from the excavation direction side, but the present invention is not limited to this. In the present invention, as in the modified example shown in FIG. 11 , the radial length of the first hard tip 3232 may be made shorter than the length of the second hard tip 3233, so that the cutting and excavation surface 3232a of the first hard tip 3232 is positioned at a position shifted radially outward from the rotation center position Pc of the cutter head 1 when viewed from the excavation direction side. In this case, the center position Pb of the center bit 323 and the rotation center position Pc of the cutter head 1 are approximately aligned when viewed from the excavation direction side (X1 direction side).

[0101] In the first and second embodiments, the center bit 23 (230) includes the second hard tip 233, which includes the tip surface 233a (second tip surface) located on the opposite side of the excavation direction from the tip surface 232b (first tip surface). However, the present invention is not limited to this. In the present invention, the center bit does not have to include the second hard tip.

[0102] Furthermore, in the above first and second embodiments, an example was shown in which the depth De of the step shape of the base material 231 (230a) of the center bit 23 (230) was smaller than half the length Lb of the first hard tip 232 in the excavation direction, but the present invention is not limited to this. In the present invention, the depth of the step shape of the base material of the center bit may be half or more the length Lb of the first hard tip in the excavation direction.

[0103] Furthermore, in the above first and second embodiments, the first hard tip 232 and the second hard tip 233 are shown as being arranged side by side in the radial direction when viewed from the excavation direction side, but the present invention is not limited to this. In the present invention, the first hard tip and the second hard tip may be arranged at positions offset from each other in the radial direction when viewed from the excavation direction side.

[0104] In the first embodiment, the third hard tip 234 has the cutting and excavating surface 234a in the excavation direction, but the present invention is not limited to this. In the present invention, the third hard tip does not have to have a cutting surface. [Explanation of symbols]

[0105] 1 cutter head 2, 202 Cutter Bit 23, 230, 323 Center Bit 100, 200 Tunnel Boring Machine 230a, 231 base material 231a Part 1 231b Part 2 232, 3232 First hard tip 232a, 3232a Cutting excavation surface (1st cutting excavation surface) 232b Tip surface (first tip surface) 232c Slope 232d Parallel surface on inner circumference side 233, 3233 Second Hard Tip 233a Tip surface (second tip surface) 234 Third Hard Tip 234a Cutting excavation surface (2nd cutting excavation surface) De Depth Pb center position Pc Rotation center position (rotation center axis) St1 step surface

Claims

1. A cutter head that excavates as it rotates, a center bit arranged on the innermost side in the radial direction of the rotation center axis of the cutter head; and a plurality of cutter bits provided on the excavation direction side of the cutter head, The center bit is A base material and a first cutting and excavating surface that is a side surface extending along a direction parallel to the radial direction and that cuts or excavates at least one of soil and sand and obstacles underground, and a first hard tip that is attached to the base material; A tunnel boring machine in which the first cutting and excavation surface of the first hard tip is positioned radially outward from the rotation center position of the cutter head so as not to include the rotation center position when viewed from the excavation direction side, and is positioned closest to the excavation direction side.

2. 2. The tunnel boring machine according to claim 1, wherein the first hard tip is arranged so as not to include the rotation center position of the cutter head when viewed from the excavation direction side.

3. 2. The tunnel boring machine according to claim 1, wherein the center bit is arranged such that, when viewed from the excavation direction side, the center position of the center bit is shifted radially outward from the rotation center position of the cutter head.

4. The first hard tip further includes a first tip surface provided on the excavation direction side of the first cutting and excavation surface, The center bit further includes a second hard tip including a second tip surface arranged on the opposite side of the excavation direction from the first tip surface, 2. The tunnel boring machine according to claim 1, wherein the second tip surface of the second hard tip is arranged so as to include the rotation center position of the cutter head when viewed from the excavation direction side.

5. 5. A tunnel boring machine as described in claim 4, wherein the base material of the center bit has a stepped shape including a first portion provided on the excavation direction side and to which the first cutting and excavation surface portion of the first hard tip is attached, and a second portion provided on the opposite side of the excavation direction of the first portion and to which the second tip surface portion of the second hard tip is attached.

6. 6. A tunnel boring machine according to claim 5, wherein the depth of the step shape of the base material of the center bit is smaller than half the length from the bottom surface of the first hard tip to the first tip surface in the excavation direction of the first hard tip.

7. 5. The tunnel boring machine according to claim 4, wherein the first tip surface of the first hard tip and the second tip surface of the second hard tip are arranged side by side in the radial direction when viewed from the excavation direction side.

8. the first portion of the base material having a step shape includes a step surface provided at a boundary portion with the second portion, 6. The tunnel boring machine of claim 5, wherein the center bit further includes a third hard tip attached to the step surface.

9. 9. A tunnel boring machine as described in claim 8, wherein the third hard tip includes a second cutting and excavation surface which is a side surface extending along a direction parallel to the radial direction and is positioned on the opposite side of the excavation direction from the first tip surface of the first hard tip.

10. The first hard tip further includes a first tip surface provided on the excavation direction side of the first cutting and excavation surface, 2. The tunnel boring machine according to claim 1, wherein the first tip surface of the first hard tip has a flat surface extending along a direction perpendicular to the excavation direction.

11. The first hard tip includes: A first tip surface provided on the excavation direction side of the first cutting and excavation surface; 2. The tunnel boring machine according to claim 1, further comprising an inclined surface provided on the radially outer periphery of the first tip end surface and inclined in a direction opposite to the excavation direction.

12. the first portion of the base material having a step shape includes a step surface provided at a boundary portion with the second portion, 6. A tunnel boring machine as described in claim 5, wherein the first hard tip is provided on the step surface and further includes an inner parallel surface extending parallel to the excavation direction from the inner side in the radial direction of the first tip surface.

Images